1. Field of the Invention
This invention relates to a liquid composition for the preparation of a permeable membrane and to a method for the manufacture of the permeable membrane. More particularly, this invention relates to a liquid composition for the preparation of a permeable membrane (hereinafter referred to "membrane") to be used as in a mechanical kidney, plasma separator, etc. and to a method for the manufacture of the membrane.
2. Description of Prior Arts
Mechanical kidneys and other devices for the filtration of body fluids operated by means of osmosis, ultrafiltration, etc. have achieved notable growth and have come to find extensive utility in the medical field. In such mechanical kidneys and other devices for the filtration of body fluids, extremely fine hollow fibers and membranes adapted for dialysis of body fluids are playing the most important role. These transmitting membranes such as hollow fibers for dialysis are represented by hollow fibers made of regenerated cellulose which is obtained by the deacetation of cellulose triacetae. The hollow fibers are deficient in water permeation capacity and, therefore, require a long time for the treatment of blood. At times, the treatment by use of such hollow fibers inevitably necessitates prolonged confinement of patients. And, such prolonged confinement possibly brings about undesirable results particularly in the case of senile patients and patients of delicate physical conditions. Hollow fibers made of cellulose esters have been proposed. Adoption of cellulose esters as the raw materials obviates the complicate work of deacetation inevitably entailed when regenerated cellulose is used as the raw material. The hollow fibers using such cellulose esters exhibit rather satisfactory water permeation capacity. When these cellulose esters are prepared in the form of dopes for spinning, however, they pose a problem of hygienic safety. In one of such dopes, for example, acetyl cellulose is used in a concentration of 30 weight percent in the mixture of acetone and formamide (40:60).
With a view to eliminating the faults found with the hollow fibers made of regenerated cellulose derived from cellulose triacetate or those made of cellulose acetate, a method for the preparation of hollow fibers has been proposed which comprises a steps of extruding the spinning dope of cuprammonium cellulose through annular spinning orifices, allowing the continuously extruded hollow tubes to fall down gravitationally and, during the descent of the hollow tubes, filling to capacity the interiors of the continuous hollow tubes formed from the dope with a liquid incapable of coagulating the spinning dope, then allowing the descending hollow tubes to be amply fluidly elongated by the gravitational pull exerted thereon, and thereafter immersing the elongated hollow tubes in a dilute sulfuric acid solution to be coagulated and regenerated (Japanese Patent Publication No. 1363/1980). Although the hollow tubes of cuprammonium cellulose thus prepared exhibit higher water transmitting capacity than those made of regenerated cellulose derived from cellulose triacetate and those made of cellulose esters, they are capable of being permeated only by low molecular compounds such as, for example, urea and vitamin B.sub.12 and incapable of being permeated by compounds of medium and high molecular weights. When they are used in a mechanical kidney, for example, they betray a disadvantage that melanin pigments and other similar matter gradually accumulate on their walls.
An object of the present invention, therefore, is to provide a liquid composition for the manufacture of a novel membrane and a method for the manufacture of the membrane.
Another object of this invention is to provide a liquid composition for the manufacture of a membrane capable of passing compounds of not merely low molecular weights but also medium and high molecular weights and a method for the manufacture of the membrane.
Yet another object of this invention is to provide a method for the manufacture of dialytic hollow fibers capable of being permeated by substances of low molecular weights and substances of medium and high molecular weights as well.